JP2009214082A - Method and apparatus of biological treatment for organic material-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make organic material-containing water subjected to a biological treatment by adding phosphorus as a nutrient, and to prevent membrane contamination in filtering with a membrane the biologically treated liquid so obtained. <P>SOLUTION: The biologically treated liquid flowed out from a biological treatment tank 21 is flocculated in a coagulation/sedimentation tank 22. The phosphoric acid concentration of the flocculated liquid obtained is measured by a densitometer 43 for phosphoric acid, with the addition of phosphoric acid adjusted so that the measurement value becomes ≤2 mg/L. The phosphoric acid is allowed to remain at ≤2 mg/L in the flocculated liquid. A phosphoric acid solution may be added to some excess so that no phosphoric acid runs short in the biological treatment in the biological treatment tank 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and apparatus for aggregating a biological treatment liquid obtained by biologically treating organic substance-containing water, and further treating the aggregation treatment liquid with a filtration membrane. In particular, the present invention relates to a biological treatment method and apparatus for organic matter-containing water discharged with the manufacture of electronic devices such as semiconductor memory devices and liquid crystal display devices.

  Conventionally, biological treatment is widely used for treatment of organic matter-containing water such as sewage containing organic matter and industrial wastewater. In the biological treatment of organic matter-containing water, the organic matter-containing water is introduced into a biological treatment tank and mixed with a microbial community called activated sludge to biologically decompose the organic matter to obtain a biological treatment solution with reduced organic matter. Since the biological treatment liquid in the state taken out from the biological treatment tank contains biological sludge composed of microorganisms, it is processed by a solid-liquid separation device such as a sedimentation basin.

  In recent years, effective use of water resources has been promoted by using a biological treatment liquid as a raw material (raw water) of pure water. In general, when pure water is produced, in order to remove salts contained in raw water, a treatment using a desalinator such as a reverse osmosis (RO) membrane device is performed. A liquid (separated liquid) obtained by solid-liquid separation of the biological treatment liquid may contain a polymer substance that clogs the membrane. For this reason, when the biological treatment liquid is reused, it is required to further clarify the separation liquid.

  Therefore, as described in Patent Document 1, the separated liquid is filtered and clarified by a membrane filtration apparatus having a filtration membrane such as a microfiltration (MF) membrane, and the obtained filtrate is desalted by, for example, an RO membrane apparatus. Processing has been developed. Such water recovery technology is widely used in factories that manufacture electronic components such as semiconductor storage devices and liquid crystal display devices, but wastewater discharged during the manufacturing of electronic components is a variety of substances that clog membranes. including.

  As a substance that contaminates the membrane, there is a polymer substance (viscous substance) generated by metabolism of microorganisms. In the method disclosed in Patent Document 1, a filtrate filtered by a membrane filtration device is introduced into an adsorption tower packed with calcium phosphate to remove polymer substances generated by microorganisms and then passed through an RO membrane device. In order to prevent the blockage of the membrane. Patent Document 2 describes that calcium used for treatment of wastewater containing hydrofluoric acid and nitrogen used in the manufacturing process of semiconductor products and liquid crystal products clogs the membrane.

JP-A-2005-238152 JP 2003-266096 A

  When collecting and reusing a biological treatment solution, it is important to prevent clogging of the membrane for stable water treatment. However, as described above, there are various factors that clog the membrane, and even when a biological treatment liquid obtained by biological treatment of electronic component manufacturing wastewater containing almost no calcium is treated with the membrane, the membrane may be clogged. .

  An object of the present invention is to prevent clogging of a membrane when the organic material-containing water containing almost no calcium, particularly an electronic component manufacturing waste water, is biologically treated and clarified with a membrane and then reused.

  The present inventor has found that the membrane, which is clogged by the phosphorous compound produced by the reaction of phosphorus, which is a nutrient source for microorganisms, with the inorganic flocculant, has completed the present invention. Specifically, the present invention provides the following.

(1) Biological treatment by adding phosphoric acid to water containing organic matter,
An inorganic flocculant is added to the biological treatment liquid obtained by the biological treatment to perform an aggregation treatment,
Measure the phosphoric acid concentration of the aggregation treatment liquid obtained by the aggregation treatment, adjust the amount of phosphoric acid added based on the measured phosphoric acid concentration,
A biological treatment method for organic matter-containing water, wherein the aggregation treatment liquid is subjected to membrane filtration.
(2) Measure the phosphoric acid concentration of the flocculation treatment solution immediately before membrane filtration,
The biological treatment method for organic matter-containing water according to (1), wherein the addition amount of the phosphoric acid is adjusted so that the phosphoric acid concentration of the aggregation treatment liquid is 0.5 mg / L or more and 2 mg / L or less.
(3) phosphoric acid addition means for adding phosphoric acid to organic substance-containing water;
A biological treatment tank for biologically treating the organic-containing water to which the phosphoric acid is added;
Aggregation treatment means for adding an inorganic flocculant to the biological treatment liquid that has flowed out of the biological treatment tank to agglomerate,
Phosphoric acid concentration measuring means for measuring the phosphoric acid concentration of the aggregating treatment liquid flowing out from the aggregating treatment means;
Adjusting means for controlling the phosphoric acid addition means based on the phosphorous concentration measured by the phosphoric acid concentration measuring means and adjusting the addition amount of the phosphoric acid;
A biological treatment apparatus for water containing organic matter, comprising membrane filtration means for membrane filtration of the aggregation treatment liquid.
(4) The phosphoric acid concentration measuring means is disposed immediately before the membrane filtering means,
The biological treatment apparatus for organic matter-containing water according to (3), wherein the adjustment unit adjusts the phosphoric acid addition unit so that a phosphoric acid concentration of the aggregation treatment liquid is 0.5 mg / L or more and 2 mg / L or less.

  ADVANTAGE OF THE INVENTION According to this invention, the clogging of the film | membrane at the time of carrying out the biological treatment of the organic substance containing water discharged | emitted in the electronic component manufacture process and hardly containing phosphorus and calcium can be prevented. In addition, according to the present invention, even if the amount of phosphorus added is not adjusted with high accuracy, the conflicting problems of biological treatment failure and membrane contamination prevention due to phosphorus shortage when biologically treating the organic substance-containing water are solved. It becomes possible to do.

  The present invention is suitable for treating organic matter-containing water, particularly wastewater discharged in the course of manufacturing electronic components and containing almost no calcium or phosphorus (hereinafter referred to as “electronic organic matter-containing wastewater”). set to target. Specifically, an electronic organic matter-containing wastewater having a calcium concentration of 1 mg / L or less, a phosphorus concentration of less than 1 mg / L, and an organic matter concentration of about 200 mg / L is a suitable treatment target. Hereinafter, a case where such electronic organic matter-containing wastewater is treated will be described as an example.

  FIG. 1 is a schematic diagram of a biological treatment apparatus 1 according to an embodiment of the present invention. The biological treatment apparatus 1 is configured by connecting a biological treatment tank 21, a coagulation sedimentation tank 22, a microfiltration (MF) membrane device 23, and a reverse osmosis (RO) membrane device 24 in this order in series.

  A raw water pipe 31 is connected to the biological treatment tank 21, and electronic organic matter-containing wastewater is introduced into the biological treatment tank 21 through the raw water pipe 31. The biological treatment tank 21 holds microorganisms that decompose organic matter (for example, aerobic activated sludge), and an aeration pipe 51 that supplies oxygen to the liquid in the tank is disposed in the tank.

  The biological treatment tank 21 preferably has a sludge concentration (MLVSS) in the tank maintained at about 2,000 to 4,000 mg / L, and the solid content separated from the liquid in the coagulation sedimentation tank 22 as necessary. Will be returned as returned sludge. In addition, when the organic matter concentration of the electronic organic matter-containing wastewater is extremely low (for example, when it is 100 mg / L or less), there is a possibility that the growth of microorganisms is reduced. If the amount of microorganisms in the biological treatment tank 21 is insufficient, organic matter decomposition cannot be performed satisfactorily. In such a case, an organic matter is added, or another organic matter-containing water with a high organic matter concentration is mixed, and biological treatment It is good to adjust so that the organic substance density | concentration of the to-be-processed water introduced into the tank 21 may be about 100-400 mg / L.

  Moreover, in this embodiment, the phosphorus density | concentration of the electronic organic matter containing waste water used as to-be-processed water is low. Since phosphorus is an essential nutrient of microorganisms, the biological treatment apparatus 1 performs biological treatment by providing phosphoric acid addition means to replenish phosphorus. Specifically, a phosphoric acid storage tank 41 and a phosphorus addition path 37 are provided as phosphoric acid addition means, and the phosphorus addition path 37 is connected to the biological treatment tank 21. A phosphoric acid solution is stored in the phosphoric acid storage tank 41, and phosphoric acid is added to the biological treatment tank 21 via the phosphorus addition path 37.

  The phosphorus addition path 37 is provided with a pump P for adjusting the addition amount of the phosphoric acid solution, and the addition amount of the phosphoric acid solution is adjusted by adjusting the number of revolutions of the pump P by adjusting means described later. The phosphorus addition path 37 may be provided with a flow rate adjusting valve, a flow path opening / closing valve or the like instead of the pump P, and the opening / closing of the valve may be controlled to adjust the phosphoric acid addition amount. The adjustment of phosphoric acid addition will be described in detail later.

  The liquid (biological treatment liquid) obtained by adding phosphoric acid and treating the waste water containing the electronic organic matter in the biological treatment tank 21 contains microorganisms, residual organic matter, and the like when taken out from the biological treatment tank 21. Yes. Therefore, the biological treatment liquid is introduced into the coagulation sedimentation tank 22 via the first liquid feeding pipe 32 connecting the biological treatment tank 21 and the coagulation sedimentation tank 22.

  The coagulation sedimentation tank 22 is connected to the coagulant storage tank 42 via the coagulant addition path 38, and these constitute coagulation processing means. In the flocculant storage tank 42, an inorganic flocculant is stored, and the flocculant is added to the biological treatment liquid from the flocculant addition path 38, and an insoluble substance is agglomerated to separate the coarse solid from the liquid. Examples of inorganic flocculants include aluminum flocculants (polyaluminum chloride, aluminum sulfate, sodium aluminate, etc.) and iron flocculants (ferric chloride, ferrous sulfate, ferric sulfate, etc.).

  The flocculant is added to the biological treatment liquid at a concentration of about 100 to 300 mg / L, and the biological treatment liquid and the flocculant are mixed by stirring with a stirrer 52 provided in the flocculation settling tank 22. The insoluble substance in the biological treatment liquid aggregated by the flocculant is coarsened, gravity settled and pulled out from the coagulation sedimentation tank 22, part is returned to the biological treatment tank 21 as return sludge, and the other part is discharged as excess sludge. The In addition, although the piping which draws out solid content is connected to the coagulation sedimentation tank 22, and the return piping which returns sludge to the biological treatment tank 21 is branched from this piping, these piping is abbreviate | omitting illustration.

  Connected to the coagulation sedimentation tank 22 is a second liquid feeding pipe 33 for taking out the liquid component separated from the solid content (coagulation treatment liquid). An MF membrane device 23 having an MF membrane is disposed at the end of the second liquid feeding pipe 33. It is not excluded to use an ultrafiltration membrane device provided with an ultrafiltration (UF) membrane instead of the MF membrane as a device for further clarifying the coagulation treatment liquid.

  In front of the MF membrane device 23 which is a membrane filtration device for clarifying the aggregation treatment liquid, a phosphoric acid concentration measuring means is provided, and the biological treatment tank 21 is based on the phosphoric acid concentration in the aggregation treatment solution sent to the membrane filtration device. The amount of phosphoric acid solution to be added during biological treatment in is adjusted. The measurement of the phosphoric acid concentration of the aggregating treatment liquid is preferably performed immediately before the membrane filtration device. In this embodiment, a fully automatic phosphoric acid concentration meter as a phosphoric acid concentration measuring means is provided at the liquid inlet to the MF membrane device 23. 43 is connected.

  In the present embodiment, the phosphoric acid concentration meter 43 serves as both a phosphoric acid concentration measuring unit and an adjusting unit. Specifically, the phosphoric acid concentration meter 43 is provided with a control circuit that generates an output signal for adjusting the rotational speed of the pump P provided in the phosphorus addition path 37 based on the measured value of the phosphoric acid concentration of the liquid to be measured. ing. When an electromagnetic on-off valve or a flow rate adjusting valve is provided in the phosphorus addition path 37, a signal for adjusting the opening / closing or opening of the valve may be configured so that the control circuit of the phosphate concentration meter 43 issues.

  The amount of phosphoric acid added is adjusted so that the phosphoric acid concentration of the aggregation treatment solution collected immediately before the MF membrane device 23 and used for the measurement of the phosphoric acid concentration is 0.5 mg / L or more and 2 mg / L or less. In this embodiment, the phosphoric acid concentration meter 43 is configured to automatically adjust the phosphoric acid addition amount, but either or both of the phosphoric acid concentration and the phosphoric acid addition amount are adjusted manually. Is not excluded. As a control circuit provided in the phosphoric acid concentration meter 43, a known microprocessor or the like is used, and an output signal for adjusting the flow rate of the phosphoric acid solution flowing through the phosphoric acid addition path 37 is generated with the measured value of the phosphoric acid concentration as an input. What is necessary is just to comprise.

  Generally, when biologically treating electronic organic matter-containing wastewater containing almost no phosphorus, as described in Patent Document 2, phosphoric acid is excessively added. It has been pointed out that the phosphoric acid added in excess and remaining in the biological treatment liquid generates calcium phosphate and clogs the membrane when calcium is present in the biological treatment liquid.

  On the other hand, when the organic organic matter-containing wastewater does not substantially contain calcium, it is predicted that calcium phosphate is not generated and clogging of the film does not occur, but even in this case, the film may be clogged, The cause investigation was requested. In response to this problem, the present inventor has found that phosphoric acid added excessively during biological treatment reacts with the inorganic flocculant to produce a substance that clogs the membrane.

  More specifically, as shown in the present embodiment, phosphoric acid added as a nutrient source for microorganisms during biological treatment remains in the biological treatment liquid, and the inorganic flocculant added to the biological treatment liquid reacts with phosphoric acid. Thus, aluminum phosphate, iron phosphate and the like are generated. The produced phosphorus compound is contained in the aggregating treatment liquid and sent to the membrane filtration device, and adheres to the membrane surface to cause clogging of the membrane.

  Therefore, in the present invention, the phosphoric acid concentration is measured immediately before membrane treatment of the aggregating treatment solution, and the amount of phosphoric acid added during biological treatment is adjusted based on this measured value. However, as described above, when phosphorus is insufficient during biological treatment, biological treatment is not performed well. Therefore, it is necessary to take care that phosphoric acid is supplied in an amount necessary for biological treatment.

  Here, when the present inventor has examined, when calcium is not substantially contained in the liquid to be treated, even if the aggregation treatment liquid contains about 0.5 mg / L of phosphoric acid, a film contaminant is generated. The risk of occluding the membrane is low. For this reason, the amount of phosphoric acid added may be adjusted so that the phosphoric acid concentration of the aggregating treatment solution is 2 mg / L or less, and excessive addition to the extent that some (less than 2 mg / L) phosphoric acid is contained. Is acceptable. Therefore, compared with the technique described in Patent Document 2 in which the phosphoric acid concentration of the liquid used for the membrane treatment is required to be adjusted to 0.5 mg / L or less, in the present invention, the addition amount of phosphoric acid is adjusted with high accuracy. There is no need to carry out the process, and the risk of poor biological treatment can be reduced by reducing the amount of phosphoric acid added too much. That is, in the present invention, it is possible to avoid the necessity of controlling the addition amount of phosphorus with high accuracy in order to solve two contradictory problems, namely, membrane clogging due to excessive addition of phosphorus and poor biological treatment due to insufficient addition of phosphorus. .

  The RO membrane device 24 is arranged at the rear stage of the MF membrane device 23. The MF membrane device 23 and the RO membrane device 24 are connected by a third liquid feeding pipe 34, and the filtrate flowing out from the MF membrane apparatus 23 is sent to the RO membrane device 24 through the third liquid feeding pipe 34. The filtrate sent to the RO membrane device 24 is desalted by the RO membrane device 24 and reused for producing pure water.

[Example 1]
In the test apparatus simulating the biological treatment apparatus 1 shown in FIG. 1, waste water containing electronic organic matter was treated. The waste water containing electronic organic matter had a calcium concentration of 0.57 mg / L, a phosphorus concentration of 0.05 mg / L, a total organic matter (TOC) concentration of 240 mg / L, and a nitrogen concentration of 5.1 mg / L. The biological treatment tank 21 retained 100 m ³ of aerobic activated sludge at a concentration of 2,000 mg / L, and returned the solid content separated from the liquid in the coagulation sedimentation tank 22 with a pump as return sludge. To the biological treatment tank 21, an activated sludge nutrient with a concentration of 20% stored in the phosphoric acid storage tank 41 from the phosphorus addition path 37 (made by Kurita Kogyo Co., Ltd., trade name “Kribreak N200”) was added. This activated sludge nutrient contains nitrogen and phosphorus, and the addition amount of the phosphoric acid solution is based on the measurement value of the phosphoric acid concentration meter 43, and the phosphoric acid concentration of the aggregation treatment liquid supplied to the MF membrane device 23 is 2 mg / It adjusted so that it might become L or less. The amount of phosphoric acid added was adjusted by adjusting the number of revolutions of the pump P provided in the phosphorus addition path 37 according to the output signal from the phosphoric acid concentration meter 43.

  In the coagulation sedimentation tank 22, polyaluminum chloride (PAC) as an inorganic coagulant was added to the biological treatment liquid at a concentration of 200 mg / L, and the coagulation treatment was performed at pH 6.5. As the MF membrane device 23 arranged in the subsequent stage of the coagulation sedimentation tank 22, a spiral type device including an MF membrane made of tetrafluoroethylene resin (PTFE) having a pore diameter of 0.2 μm was used. The aggregation treatment liquid was supplied to the MF membrane device 23 with a water supply pressure of 0.1 MPa. As the RO membrane device 24 at the rear stage of the MF membrane device 23, a spiral-type device including a polyamide RO membrane was used, and water was supplied at a water supply pressure of 1.47 MPa.

  In Example 1, the treatment was continued for 60 days under the above conditions, and a filtrate could be obtained at a flow rate of 1 ton / hour per membrane module of the MF membrane device 23 with the above-mentioned feed water pressure.

[Comparative Example 1]
In Comparative Example 1, the phosphoric acid solution addition amount control based on the measurement value of the phosphoric acid concentration meter 43 was stopped. Others treated the waste water containing electronic organic matter under the same conditions as in Example 1. In Comparative Example 1, the phosphoric acid concentration of the aggregation treatment liquid measured with the phosphoric acid concentration meter 43 was 5 to 20 mg / L, and the average value was 10 mg / L. In Comparative Example 1, the membrane was contaminated during the experiment period of 14 days, and after 4 days, the feed water pressure to the MF membrane device 23 increased to 0.25 MPa, and the flow rate per membrane module was 0.1 ton / Fell in time.

[Reference Example 1]
As Reference Example 1, the phosphoric acid solution addition amount was adjusted so that the phosphoric acid concentration of the aggregation treatment liquid supplied to the MF membrane device 23 was 0.5 mg / L or less. As a result of treating the organic organic matter-containing wastewater under the same conditions as in Example 1, the water supply pressure to the MF membrane device 23 after 3 days from the start of the experiment was 0.06 MPa, and the flow rate per membrane module was 1 Ton / hour.

[Reference Example 2]
As Reference Example 2, the phosphoric acid solution addition amount was adjusted so that the phosphoric acid concentration of the aggregation treatment liquid supplied to the MF membrane device 23 was 1.0 mg / L or less. As a result of treating the organic organic matter-containing wastewater under the same conditions as in Example 1, the water supply pressure to the MF membrane device 23 after 3 days from the start of the experiment was 0.06 MPa, and the flow rate per membrane module was 1 Ton / hour.

[Reference Example 3]
As Reference Example 3, the phosphoric acid solution addition amount was adjusted so that the phosphoric acid concentration of the aggregation treatment liquid supplied to the MF membrane device 23 was 2.0 mg / L or less. As a result of treating the organic organic matter-containing wastewater under the same conditions as in Example 1, the water supply pressure to the MF membrane device 23 after 3 days from the start of the experiment was 0.06 MPa, and the flow rate per membrane module was 1 Ton / hour.

[Reference Example 4]
As Reference Example 4, the phosphoric acid solution addition amount was adjusted so that the phosphoric acid concentration of the aggregation treatment liquid supplied to the MF membrane device 23 was 2.2 mg / L or less. In other cases, the organic organic matter-containing wastewater was treated under the same conditions as in Example 1. As a result, the water supply pressure to the MF membrane device 23 after 3 days from the start of the experiment was 0.13 MPa, and the flow rate per membrane module was 0. It was 8 tons / hour.

  From these reference examples, when the phosphoric acid concentration of the aggregating treatment liquid exceeds 2.0 mg / L, the membrane contamination rapidly progresses. On the other hand, if the phosphoric acid concentration of the aggregating treatment liquid is 2.0 mg / L or less, the membrane It has been shown that no rapid contamination occurs. Therefore, it was shown that some excessive addition of phosphoric acid can be tolerated in order to prevent insufficient supply of phosphoric acid.

  The present invention can be used for the treatment of organic substance-containing water discharged in the electronic component manufacturing process.

The schematic diagram of the processing apparatus which concerns on one embodiment of this invention.

Explanation of symbols

1 Biological treatment device 21 Biological treatment tank 22 Coagulation sedimentation tank (coagulation treatment means)
23 Microfiltration membrane device (membrane filtration means)
24 Reverse osmosis membrane device 37 Phosphorus addition path (phosphoric acid addition means)
38 Flocculant addition path (aggregation treatment means)
41 Phosphoric acid storage tank (phosphoric acid addition means)
42 Coagulant storage tank (coagulation treatment means)
43 Phosphoric acid concentration meter (phosphoric acid addition means and adjustment means)
P pump (phosphoric acid addition means and adjustment means)

Claims (4)

Biological treatment by adding phosphoric acid to water containing organic matter,
An inorganic flocculant is added to the biological treatment liquid obtained by the biological treatment to perform an aggregation treatment,
Measure the phosphoric acid concentration of the aggregation treatment liquid obtained by the aggregation treatment, adjust the amount of phosphoric acid added based on the measured phosphoric acid concentration,
A biological treatment method for organic matter-containing water, wherein the aggregation treatment liquid is subjected to membrane filtration. Immediately before membrane filtration, measure the phosphoric acid concentration of the aggregation treatment liquid,
The biological treatment method of organic substance-containing water according to claim 1, wherein the addition amount of the phosphoric acid is adjusted so that the phosphoric acid concentration of the aggregation treatment liquid is 0.5 mg / L or more and 2 mg / L or less. Phosphoric acid addition means for adding phosphoric acid to water containing organic matter,
A biological treatment tank for biologically treating the organic-containing water to which the phosphoric acid is added;
Aggregation treatment means for adding an inorganic flocculant to the biological treatment liquid that has flowed out of the biological treatment tank to agglomerate,
Phosphoric acid concentration measuring means for measuring the phosphoric acid concentration of the aggregating treatment liquid flowing out from the aggregating treatment means;
Adjusting means for controlling the phosphoric acid addition means based on the phosphorous concentration measured by the phosphoric acid concentration measuring means and adjusting the addition amount of the phosphoric acid;
A biological treatment apparatus for water containing organic matter, comprising membrane filtration means for membrane filtration of the aggregation treatment liquid. The phosphoric acid concentration measuring means is disposed immediately before the membrane filtering means,
The biological treatment apparatus for organic matter-containing water according to claim 3, wherein the adjustment means adjusts the phosphoric acid addition means so that a phosphoric acid concentration of the aggregation treatment liquid is 0.5 mg / L or more and 2 mg / L or less.

Images